1. Field of the Invention
The present invention relates to a position sensor. It is applicable both to an angular sensor detecting rotation of one body relative to another, and to a linear sensor detecting linear movement.
2. Summary of the Prior Art
In my European patent application No. EP-A-0100243 (corresponding to U.S. Pat. No. 4,572,952) I disclosed a position sensor in which binary and bar pattern tracks on a scale act on a detector of sensitive elements in a two dimensional array. Each sensitive element detects the overlap between itself and an indicium of the track (for a bar pattern, each bar of the pattern, whether light or dark, forms an indicium). The signals generated by the sensitive elements of the detector are processed by computer correlation to yield precise data regarding the position of the tracks, and hence the scale, relative to the detector. The scale is preferably the optical image of a pattern of markings on one body, with the detector being mounted on another body, so that the relative positions of the two bodies may be determined.
Computer processing of the signals from the sensitive elements requires analogue-to-digital conversion, is inconveniently time consuming, and greatly increases the size of the sensor. The present invention therefore seeks to overcome, or at least ameliorate, these problems.